In a nutshell: Vaccinating mothers during the third trimester of pregnancy would be the most effective way to protect infants against pertussis, health officials from the California Department of Public Health have said.

Infants are among the hardest hit in California’s ongoing pertussis epidemic. Because they are too young to be effectively vaccinated and are therefore dependent on maternal antibodies for protection, the most effective strategy to protect infants is to make sure all pregnant women receive the tetanus, diphtheria, and acellular pertussis vaccine (Tdap) in the third trimester of pregnancy. This timing will ensure the maximum transfer of protective maternal antibodies to the infant, wrote lead author Kathleen Winter and her colleagues in the US Centers for Disease Control and Prevention’s Morbidity and Mortality Weekly Report.1

“Since the immune response to Tdap peaks about two weeks after administration and the majority …